1986 Toyota MR2 - an uncontrollable evacuation of the bowels

Aw, shame, you didn't get the ones with the little curved ends for grabbing onto hoses, too? They're really handy for mangling rubbish in inaccessible spots!

I have a dream that one day this car will be back on the road.
‘Hopeless’ I hear you say. Well, we will see about that.

The engine hasn’t turned over since the fuel pump got stuck and that was ages ago. Years probably. Does it still turn over? Does it still have compression?

I stuck a ratchet on the crank pulley bolt and, yes it turns. I also counted four healthy compressions.
James breathes a sigh of relief.

All the oil will be in the sump so it’s a good time to change it and put a new filter on.





Once I had fresh oil installed I put the battery back on (freshly charged) and cranked the engine over to see if it’d build oil pressure.
Well, it wouldn’t crank. There was a clunk from the starter and all the dash lights went out. They didn’t come back on when I let go of the key either.
I tried a few times and it was the same story. So off I went to find my multimeter.

The plan was to flick it to start, have the power fail and leave it in that state while I went on a hunt. Except this time it cranked. Hmmm. I suspect I had a dirty relay that’s cleaned itself. I’ll have to keep an eye on that. I think I have some spare relays somewhere. Might be worth chucking one in the glovebox.

Anyway, engine cranked for a while and eventually the oil pressure started to come up.





I remember debating how best to store the fuel pump after I freed it up. In the event I chucked it in a plastic bag, lobbed it in a cardboard box and forgot about it. As it turned out this apparent negligence turned out to be a well thought out plan concocted by a world renowned genius. (Yes, I’m talking about me!) Also very handsome and modest, or so people say.
Where was I? Oh yes, the pump still worked so I assembled the tank and popped it by the car for fitting.





You know the rest. Ten minutes to get it in position and then a couple of days of bruised knuckles trying to get all the pipework connected. I think I used an entire years allocation of curses and will now have to live the life of a saint as a result.

Say goodbye to the date on the tank. It’ll be hidden for the foreseeable future. At least I really hope it will.





It was worth the week of effort to do that.
I’ve got a new Toyota fuel filter to go on (astronomically expensive from what I remember) but I’ll run the engine first just in case it sucks a load of crud out of the tank. I mean the tank is very clean looking and if it does suck up crud it’ll block the filter on the pump and the tank will have to come out again and you’ll see that date again…


Next we can reassemble the fuel cap door bits.





The springy thing, the latch, and all that plastic stuff round the neck got cleaned and fitted.
Yeah, I’ve used stainless cap screws to bolt it together. It won’t lose me any points at the concours car show because, by the time they’ve looked at the rest of the car there won’t be any points left to lose.


I have a small problem in that when the door is on the catch it’s a little proud.





It looks a lot worse in the photo than it does in person but it still needs tweaking. I can’t see how to adjust it though. Apart from just bending the frame of the door which might be how it’s done. Does anybody know?


The head light switch had been knocked on so when I connected the battery the pop up lights popped up. Well one of them did. The other got half way and got stuck. I had noticed that one light was getting lazy when I last drove the car. I guess the gear box needs cleaning and lubricating.





Ok… So here’s another thing I don’t understand.
That assembly looks like it should just unbolt from the car. Two bolts and two nuts in the front trunk and one bolt lower under the car. Then it should just come off the car. But it doesn’t.
The studs attached to the bracket need it to go directly forwards but the motor needs it to go forwards and down at about 45 degrees. It won’t do both so you have to take the motor off the bracket to get it off the car.

I don’t for a minute believe they built this up on the car when they built it but I can’t work out how they got it on the car in one piece. It don’t not make no sense it don’t not.

It wasn’t the gearbox. It was the hinge that the light swings up on that was rusted solid. You can’t disassemble it so I just had to lubricate and exercise it until it freed up.





It’s now quicker than the left side so I might have to do something with that one day. I’ve oiled it for the time being. Actually both lights need restoring before they rust away. But not tonight Josephine.

James

Maybe a bit of a sharp tap & a shake will wake up the low warning lamp unit?

I thought I’d check that fuel tank empty light before I put the centre console back in. Just to see if I could make it work.
Sadly the gauge was still less than perfect so I thought I’d look at that first.


By putting a multimeter across the sender I should read a smoothly changing resistance as I sweep the float through its ark. But I didn’t. It was twitchy and in places went open circuit.
I think there were two reasons for this. Firstly the wire wound resistor that the arm sweeps across looked dirty so I ‘polished’ it with an abrasive pad. One of those that you use for keying paint.

The second problem is that the electrical circuit runs through the hinge of the arm just by the metal to metal contact where the arm sits in the holder. I’d cleaned it by exercising it but not enough so I thought I’d add a thin wire across the joint.





And now I’m getting better results with the multimeter and the gauge reads full when fitted to the tank. The tank pretty much is full so that’s good.

Back to that tank empty light then.
I thought this might be some sort of tiny float switch.





I wasn’t totally convinced by this idea because fuel empty warning lights are very reliable and I wasn’t convinced that a microscopic float switch would work that well.
There are three pin holes in the top and bottom of this to let the petrol in. When I poked something in them I couldn’t feel a float. More over, when I held it up to the light I could see right through the can. So there is no float in there.
Right… Well… Yeah… So how does this actually work then?


Well it turns out that there are no moving parts at all. The only thing in the can is a Negative Temperature Coefficient Thermistor. Otherwise known as an NTC.

Aw, come on James, speak English please!

An NTC is just a resistor whose resistance changes with temperature. If it’s cold then its resistance goes up. If it’s hot its resistance does down.
The low fuel warning light circuit is simple.





So…
If the NTC is hot then its resistance is low and the light is on.
If the NTC is cold then its resistance is high and the light goes out.

Great. And how does that measure the level of fuel in the tank?

The thing I haven’t mentioned is that the current through the circuit actually heats the NTC up. That means that its normal state in air is with the NTC hot, its resistance is low and the light is on.
But dunk it in a tank of petrol and the fuel cools it down. Its resistance goes up and the light goes out.

It’s a very simple circuit. It’s really very clever. And broken.
If I short the two sides of the little capsule the low fuel light comes on so I know everything is working apart from the NTC. If I measure the NTC with a multimeter I should see some ohms but I see an open circuit. So I guess my NTC has packed up.

You can buy the little capsule from the interwebz so I might get one and try and replace it. But not just yet. I want to get the car back on the road at some time before the universe ends.

So I bunged the centre console back in…





Loaded period tapes into the tape holder…





…And spent a while listening to music which made me happy.

James

Thanks Jimi. I wondered about prying the capsule apart to see what was in it but, oddly for me, thought better of it.
Interesting that the chap swapped the actual thermistor.

When I looked I can see the capsules for sale. Some of them were listed for bikes though. I think the critical bit is the resistance which will be related to the voltage of the system.

Anyway, that fills in a lot of the background so thanks for digging that out.
I'll look at it again at some point in the future. I'd like it to work just because I like things to work.

James

Seen that before, something to do with the rear pillar vent IIRC. Let me check the EPC

Good grief jimi I do believe you are right. It'd go over this hole...





Well I've buried that behind plastic trim and aren't about to take it apart again.
However I do think I'll have to be in there at some point in the future because the trim round the windows isn't looking too healthy and will need another go.

Thank you. I hadn't a clue where it went.

James

That sounds like it should be the title of the next Cold Play album. I'll ring Chris Martin later and give him the idea.

Also James

The first rule of electroplating is - You do not talk about electroplating.

Rules are there to be broken right? Good. Let’s talk about electroplating.
This is what we are going to plate.





The thing on the left is a bracket that holds a couple of cables onto the bottom of the fuel tank and is stopping me buttoning up the bottom of the car.
The bit in the middle is the new door switch design.
And the three bolts on the right hold the plastic liner into the left side rear wheel arch.

The first rule of electroplating is that things have to be scrupulously clean. That starts with sandblasting the bejesus out of the bits.





Then you need to clean them even more so they get dunked in acid for a couple of minutes.





The metal bits fizz for a while. Generally acid is not something you want to get on your hands so rubber gloves are the required fashion. Green ones in my case as it matches my natural aura.

After a minute or two in acid they get rinsed off and go in the zinc plating tank.





It probably shouldn’t look like tea. It probably needs running through a coffee filter to clean it up but it’s working ok so I’m not in a desperate hurry to do it.
You have to calculate the plating current before you do this. You work out the surface area of all the stuff then set a plating current of 100mA for every square inch. I think I had about 1.7 Amps for these few bits.
It sits in the tank for 20 or 30 minutes. I always move the bits around in the tank every few minutes. I do it to knock bubbles off the parts although if you have so much current that you are forming bubbles you’ll likely get a rubbish finish anyway. But also to reorient the parts with respect to the electrodes. It stops them being shaded by other bits in the tank. And… By jiggling them a bit I can hopefully shift them on the hanging wires to get better coverage.

Anyway, after 20 or 30 mins they get swilled off in water again and go into the final tanks. Passivating.
This is where you can add colour to the zinc coating. I wanted the door switch to have a silver finish and the bracket and bolts to have a yellow finish so I had both passivate tanks out.

About 60 secs in this tank will give a silver finish. Longer and it’ll start taking slight blue tint.





And this tank has a yellow die in it for the yellow finish.





Again about 60 seconds. The longer it’s in there the deeper the colour. Take it out when it looks good.

Lastly another rinse in water and we get to enjoy the fruits of our labours.





You’ve done a nice job I reckon. You should be proud of that. Take the rest of the day off and tell the boss I said it was ok.


James